This invention relates to brick and brick assemblies for use in a refractory lining wherein the lining is subject to thermal stresses which result in unwanted distortion of the lining.
Maintaining stability of refractory lining structures during the life of a furnace has been an age-old problem. Due to expansion of the refractory caused by heating and cooling or permanent growth caused by alteration of the refractory, a wall constructed of refractories tends to distort from the original dimensions. This often compromises the ability of the lining to contain molten metals or gases within the confines of the furnace. Numerous designs for interlocking brick have been devised to improve wall stability. Simple methods such as use of a common tongue and groove was first proposed in 1882 and was protected by U.S. Pat. No. 260,155. This concept was later expanded and applied to a complex structure as shown in U.S. Pat. No. 308,577. U.S. Pat. No. 4,008,997 illustrates a rather unique design for building a refractory box using individual members which have opposing male and female ends. Interlocking structures for refractory shapes designed to convey hot furnace gases are shown in U.S. Pat. Nos. 3,630,503, 4,436,144 and 4,940,081. These patents all show modification of the tongue and groove concept. The refractories interlock by a series of raised projections fitting into corresponding recesses. In all three cases, the brick are stacked in a vertical fashion and have longitudinally aligned holes for transport of the hot furnace gases.
U.S. Pat. No. 4,900,249 describes a novel approach for stabilizing the critical area on the wall of an aluminum reverberatory furnace. In this patent wall block are positioned standing on end. The working face block is interlocked with the backup block by means of a male projection on the working face block which fits into a corresponding female recess in the backup block. The working face block is thus structurally tied into the backup lining with minimal joints exposed at the working face.
While the prior art has improved wall stability by making advances in the way that brick are interlocked further improvements are desired, especially since metallurgical furnaces and other high temperature vessels are expected to last longer due to the high cost of replacing the linings and the economic need to keep these furnaces and vessels in continuous operation. Wall stability is an especially acute problem in furnaces having long axial construction such as rectangular-shaped non-ferrous reverberatory furnaces. These furnaces typically have walls about 30 feet in length. Such walls, without sufficient structural support, tend to bow inward over time thus causing premature failure of the lining.